#include <bits/stdc++.h>
using namespace std;
#define int long long
#define INF 1e18
int n;
vector<int> p, dp;
vector<vector<int>> adj;
void dfs(int u) {
dp[u] = p[u];
for (int v : adj[u]) {
dfs(v);
if (dp[v] >= 0) dp[u] += dp[v];
}
}
void solve() {
int n;
cin >> n;
p.resize(n + 1); dp.resize(n + 1);
adj.resize(n + 1);
cin >> p[0];
for (int i = 1; i <= n; i++) {
int dep; cin >> p[i] >> dep;
adj[dep].push_back(i);
}
dfs(0);
cout << dp[0] - p[0];
}
int32_t main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
solve();
return 0;
}
